PhD Candidate Bio – Francis Sullivan
Francis Sullivan is a PhD Candidate and part time student in the Otto H. York Department of Chemical, Biological and Pharmaceutical Engineering at New Jersey Institute of Technology. He is also an employee of the U.S. Army Armament Research, Development and Engineering Center, Picatinny Arsenal, NJ. His research interests include mathematical modeling and computational simulation of heterogeneous reactions used in the industrial scale manufacture of energetic materials for propellant formulations.
The objective of this research effort is to develop a model for the large scale nitration of wood pulp slivers that accounts for the effects of the cellulose raw material properties on reaction kinetics and diffusion within these heterogeneous nonwoven fibrous mat structures (Figure 1).
Figure 1: Cellulose Fiber Structure
Nitrocellulose (NC) is used extensively in propellants for military applications. Traditional NC manufacturing processes involve reaction of fibrous mat structures (sheeted wood pulp or baled cotton linters) in mixtures of nitric acid, sulfuric acid, and water. This multiphase reaction (Figure 2) is normally carried out in industrial-scale batch or continuous stirred tank reactors followed by a series of stabilization operations that are used to separate the mixed acid from the reacted material. While an attempt is made to control the reaction conditions to achieve desired nitrogen content, density, and viscosity in the resulting nitrocellulose, this predictability is generally not achieved due to variations in the cellulose source materials which may affect mass transfer and reaction rates during the nitration and stabilization processing steps.
Figure 2: Synthesis of Nitrocellulose
Cellulose manufacturers have generally resorted to identifying commercially available cellulose materials that can accommodated by existing manufacturing processes given the lack of a rigorous theoretical basis relating cellulose characteristics such as morphological and compositional variation to process performance. These characteristics may depend on the cellulose source, pulping methods, and finishing processes employed in the manufacture of cellulose sheets or bales, and can introduce variability into the manufacturing process.
Through describing the effect of these characteristics on the phenomena of mass and energy transport and chemical reaction in a nitrating wood pulp sliver, processing conditions such as acid concentrations, agitation conditions, reaction temperature, stabilization temperature, etc. can be identified to optimize nitrocellulose yield and conversion for various pulp sources. Development of an unsteady, three-dimensional model to describe simultaneous mass and energy transport and chemical reaction in these nonwoven fibrous mat structures will provide a predictive tool to identify appropriate processing conditions for alternate cellulose raw materials while minimizing the need for costly and time-consuming experimentation.